Patent GB-874357-A (GB)
Title: Improvements in or relating to diaphragm carburettors
IPC: F02M9/06
Filed: 1959-12-04
Abstract: 874,357. Spray carburetters. TILLOTSON MANUFACTURING CO. Dec. 4, 1959 [Dec. 16, 1958], No. 41232/59. Class 7(3). A carburetter comprises, a body 10, Figs. 2 and 4, formed with a mixing passage 12, a throttle valve 26 movably disposed in the mixing passage, a fuel chamber 32, a flexible diaphragm 34 forming a wall of the fuel chamber, a fuel inlet 72 for admitting fuel from a supply into the fuel chamber 32, valve means 76, 77 associated with the fuel inlet, means actuated by movement of the diaphragm 34 for controlling the valve means 76, 77, a fuel discharge orifice 42 opening into the mixing passage for delivering fuel from chamber 32 into the mixing passage 12, a fuel passage between orifice 42 and chamber 32, a fuel metering means 90 movable to vary the fuel flow through the passage, and an operative connection 104, 109 between the throttle valve 26 and the metering means 90 whereby the relative position of the metering means is controlled by movement of the throttle. A choke valve mounted on shaft 20 is provided in the air inlet 18. The flexible diaphragm 34, through a lever 56 biased by spring 81, controls an inlet valve member 64 having a valve portion 77 co-operating with a seat 76 for regulating the fuel flow into the chamber. The throttle shaft is formed with a cam surface 106 which cooperates with a rod 104 to move a member 109 which controls the position of metering means 90 slidable in bore 82. Fuel flows from chamber 32 through duct 83, into bore 82, and is metered by the needle part 94 into bore 84 wherefrom it travels to the outlet 42 by means of passages 80, and 44. An air bleed may be provided from bore 82 to the air inlet 18. On opening the throttle a sub-atmospheric pressure is formed in the mixing passage 12 and the diaphragm 34 moves upwards due to atmospheric pressure acting, through aperture 39 in cover 38, on the lower side, thus allowing fuel to enter from inlet 72. Fuel flows from the chamber past the metering means opened by the throttle to the outlet 42 and into the mixing passage. In another embodiment, Figs. 6 and 8, the fuel flows from fuel chamber 321 via a duct into bore 138, and is metered by needle 132 into well 139, via passage 152. An idling orifice 146 and a slow running orifice 148 are provided at the side of throttle valve 261 which is connected as described above to metering means 128. When the orifices 146, 148 are in use, air passing through the main orifice 140 as well as the air bleed 156 from the air inlet to bore 138, mixes with the fuel. A modification of this embodiment is described wherein an auxiliary metering device independent of the throttle acts on fuel passing direct from the fuel chamber to the idling and slow speed orifices. In another embodiment, Fig. 17, a barrel-type throttle means 256 is associated with the needle 268 for metering the fuel from chamber 218 to the outlet 276. An air bleed is provided by passage 308 with restriction 310. The throttle 256, spring- loaded in bore 254, is controlled by cable 260 attached to the throttle. Adjustment of the metering means relative to the throttle 256 is provided by grooves in the member 266 which engage disc 274. Specifications 833,036 and 854,216 are referred to.